Electron beam and rf characterization of a low-emittance X-band photoinjector -: art. no. 090101

Detailed experimental studies of the first operation of an X-band (8.547 GHz) rf photoinjector are reported. The rf characteristics of the device are first described, as well as the tuning technique used to ensure operation of the 1 1/2-cell rf gun in the balanced pi -mode. The characterization of the photoelectron beam produced by the rf gun includes: measurements of the bunch charge as a function of the laser injection phase, yielding information about the quantum efficiency of the Cu photocathode (2 x 10(-5) for a surface field of 100 MV/m); measurements of the beam energy (1.5-2 MeV) and relative energy spread (Delta gamma/gamma (o) = 1.8 +/- 0.2%) using a magnetic spectrometer; measurements of the beam 90% normalized emittance, which is found to be epsilon (n) = 1.65 pi mm mrad for a charge of 25 pC; and measurements of the bunch duration (<2 ps). Coherent synchrotron radiation experiments at Ku-band and Ka-band confirm the extremely short duration of the photoelectron bunch and a peak power scaling quadratically with the bunch charge.